Re: [PATCH 1/5] I2C driver for MXC

[Sascha Hauer <s.hauer-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>]

On Mon, Mar 30, 2009 at 11:26:31AM +0200, Guennadi Liakhovetski wrote:
> Hi Darius,
> 
> On Mon, 30 Mar 2009, Darius Augulis wrote:
> 
> > I tested your driver on i.MXL with OV7670 and MT9V111 cameras. I confirm it
> > works.
> 
> Thanks for testing!
> 
> > In otherside, my driver is also tested with OV7670, MT9V111, OV7720 cameras,
> > PCF8575 expander and NT7651 LCD controller. All these devices work connected
> > to i.MXL.
> > If you have problems on MX3 only with single device, it may be caused by
> > some specific conditions.
> > I don't know it is good idea to replace one driver by another, because we
> > don't know where is the problem exactly.
> > Of course would be fine to watch your I2C bus with oscilloscope. So you
> > could see what is wrong.
> > IMO we should find what is wrong in my driver, to have good working driver
> > for all MXC SoC's.
> > If we replace it by your driver, we miss lot of ML comments fixed and
> > probably we will receive errors and problems in some different situation.
> 
> Well, I have been able to get your driver to at least pass the 
> initialisation with mt9t031 (other parts are missing yet for a complete 
> test). For that I used this silly patch:
> 
> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> index 3296380..46e1033 100644
> --- a/drivers/i2c/busses/i2c-imx.c
> +++ b/drivers/i2c/busses/i2c-imx.c
> @@ -371,6 +371,8 @@ static int i2c_imx_xfer(struct i2c_adapter *adapter,
>  	if (result)
>  		goto fail0;
>  
> +	msleep(2);
> +
>  	/* Start I2C transfer */
>  	i2c_imx_start(i2c_imx);
> 
> As you understand, this cannot be the final fix. We have to understand why 
> a delay is needed there and how long it actually has to be...
>  

Have you checked the value of disable_delay in Darius' driver or tried to
increase it?

BTW I just realized that the handling of disable_delay in Darius' driver
is wrong. This should be a per device variable.

Sascha

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